In development and manufacturing of mechanical objects, inspection of components may be automated by the use of computer systems analyzing digital images of components captured by digital cameras (using Machine Vision software). Machine Vision is the art of processing images using a computer. Until now, analyzing z-axis feature height using digital images taken by a camera from a position on the z-axis has been problematic. An example of an inspection problem would be two similar features that only differ in their height and when looking from above at the parts they appear to be identical. To detect the difference in their z-axis heights when the image is taken along the z-axis, a 2D image doesn't currently enable the machine vision tool to determine the Z value (height) of features. All features appear to be on the same flat surface of the 2D image.
U.S. Pat. No. 6,975,764: “Fast high-accuracy multi-dimensional pattern inspection” Filed Sep. 8, 2003, incorporated herein by reference teaches a method and apparatus are provided for identifying differences between a stored pattern and a matching image subset, where variations in pattern position, orientation, and size do not give rise to false differences. The invention is also a system for analyzing an object image with respect to a model pattern so as to detect flaws in the object image. The system includes extracting pattern features from the model pattern; generating a vector-valued function using the pattern features to provide a pattern field; extracting image features from the object image; evaluating each image feature, using the pattern field and an n-dimensional transformation that associates image features with pattern features, so as to determine at least one associated feature characteristic; and using at least one feature characteristic to identify at least one flaw in the object image. The invention can find at least two distinct kinds of flaws: missing features, and extra features. The invention provides pattern inspection that is faster and more accurate than any known prior art method by using a stored pattern that represents an ideal example of the object to be found and inspected, and that can be translated, rotated, and scaled to arbitrary precision much faster than digital image re-sampling, and without pixel grid quantization errors. Furthermore, since the invention does not use digital image re-sampling, there are no pixel quantization errors to cause false differences between the pattern and image that can limit inspection performance.
U.S. Pat. No. 6,850,646 “Fast high-accuracy multi-dimensional pattern inspection” Filed Nov. 10, 2003 and incorporated herein by reference teaches a method and apparatus are provided for identifying differences between a stored pattern and a matching image subset, where variations in pattern position, orientation, and size do not give rise to false differences. The invention is also a system for analyzing an object image with respect to a model pattern so as to detect flaws in the object image. The system includes extracting pattern features from the model pattern; generating a vector-valued function using the pattern features to provide a pattern field; extracting image features from the object image; evaluating each image feature, using the pattern field and an n-dimensional transformation that associates image features with pattern features, so as to determine at least one associated feature characteristic; and using at least one feature characteristic to identify at least one flaw in the object image. The invention can find at least two distinct kinds of flaws: missing features, and extra features. The invention provides pattern inspection that is faster and more accurate than any known prior art method by using a stored pattern that represents an ideal example of the object to be found and inspected, and that can be translated, rotated, and scaled to arbitrary precision much faster than digital image re-sampling, and without pixel grid quantization errors. Furthermore, since the invention does not use digital image re-sampling, there are no pixel quantization errors to cause false differences between the pattern and image that can limit inspection performance.
U.S. Pat. No. 4,650,333 “System for measuring and detecting printed circuit wiring defects” Filed Apr. 12, 1984 incorporated herein by references teaches a non-contact system for detecting printed circuit wiring defects and for measuring circuit feature height relative to a substrate. The system has an energy source for illuminating the substrate and circuit features and a scanner for both instantaneously receiving energy reflected from the substrate and circuit features and for generating a signal in response to the reflected energy, which signal is adapted to vary with the intensity of the reflected energy. An analyzer is connected to the scanner for correlating the generated signal to a measurement representative of the height of the circuit features relative to the substrate. Variations and non-uniformity of the substrate surface due to bending, warpage or other causes can be accounted for so as to provide an accurate measurement of the height of a circuit feature relative to the substrate surface on which it is mounted.
U.S. Pat. No. 6,603,103 “Circuit for machine-vision system” Filed Aug. 7, 1999 incorporated herein by reference teaches manufacturing lines include inspection systems for monitoring the quality of parts produced. Manufacturing lines for making semiconductor devices generally inspect each fabricated part. The information obtained is used to fix manufacturing problems in the semiconductor fab plant. A machine-vision system for inspecting devices includes a light source for propagating light to the device and an image detector that receives light from the device. Also included is a light sensor assembly for receiving a portion of the light from the light source. The light sensor assembly produces an output signal responsive to the intensity of the light received at the light sensor assembly. A controller controls the amount of light received by the image detector to a desired intensity range in response to the output from the light sensor. The image detector may include an array of imaging pixels. The imaging system may also include a memory device which stores correction values for at least one of the pixels in the array of imaging pixels. To minimize or control thermal drift of signals output from an array of imaging pixels, the machine-vision system may also include a cooling element attached to the imaging device. The light source for propagating light to the device may be strobed. The image detector that receives light from the device remains in a fixed position with respect to the strobed light source. A translation element moves the strobed light source and image detector with respect to the device. The strobed light may be alternated between a first and second level.
U.S. Pat. No. 6,052,189 “Height measurement device and height measurement method” Filed Aug. 11, 1997 incorporated herein by reference teaches a height measurement device that can accurately measure the height of an object to be measured, and that can easily and precisely adjust the focal point of an optical system. According to the present invention, a height measurement device, which forms an image of a light point generated by a light source on a surface of a measured object via an irradiation side focusing lens, which forms an image of the formed image of the light point on a light point position detector via a light reception side focusing lens, and measures a height of the measured object according to the light point position on the light point position detector, comprises: a stage perpendicularly movable with the measured object mounted thereon; a camera for obtaining a light point image formed on a target face on the stage; and a controller for detecting a position of the stage or of the radiation focusing lens as a focal point, at which a light quantity on a predetermined pixel in the light point image obtained by the camera becomes a maximum level, while moving the stage or the irradiation side focusing lens.
None of these methods solves the problem of detecting feature height defects using a captured image of an object.